JP2002281522A - White balance controller and digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white balance controller and a digital camera, with which a user can easily set/change achromatic setting in the case of white balance control. SOLUTION: In the white balance controller, with which data provided from an imaging device are converted to color difference data, an achromatic color is decided by dividing these color difference data into a plurality of areas and white balance is controlled by controlling the gain quantity of color data on the basis of pixel data in the area decided as an achromatic color, this device is provided with a means for designating and photographing an object considered as an achromatic color and a means for setting an area portion corresponding to the color difference data in the photographed data of this designated object as an achromatic color extraction range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital camera,
The present invention relates to a white balance control device in a video camera, an image capturing device, and the like. In particular, it relates to region setting for achromatic color range extraction.

[0002]

2. Description of the Related Art In a digital camera, a digital video camera or the like, it is necessary to adjust a white balance in order to obtain a high quality color image. If this white balance is lost, not only will the color of the captured image be colored when capturing a white object, but also the color reproducibility will deteriorate when a general object is captured. Can not be obtained. A technique related to such white balance adjustment is to divide a color space into a plurality of color spaces and calculate a distribution in each color region of a subject, as in the technique disclosed in Japanese Patent Application Laid-Open No. 5-292533. Is detected and adjusted. In general, when extracting achromatic colors, there is a low probability that a situation where there are multiple light sources with different color temperatures in one image will occur, and achromatic color shift due to the color temperature of the light source may occur uniformly. It is thought that there are many. However, when there is a color similar to the change in color temperature in an image, the peak of the distribution of data determined to be achromatic appears at a plurality of locations, and in many cases data as if there are a plurality of light sources is obtained. is there. In such a case, in the above-described related art, since the integrated value of all data in the achromatic color extraction range is used for white balance adjustment, accurate white balance adjustment may not be achieved. This problem is the same even when an image is divided into a plurality of regions and handled. to solve this problem,
JP-A-10-210495, JP-A-11-205
According to the techniques disclosed in Japanese Patent Application Laid-Open No. 812 and Japanese Patent Application Laid-Open No. H11-308634, the achromatic color extraction range is set flexibly and finely, and even for image data in which the peak of the distribution of data determined to be achromatic appears at a plurality of locations. The achromatic color extraction error is reduced, and it is possible to flexibly cope with various photographing conditions of an image and to perform high-precision white balance adjustment. In addition, as a setting method at the time of white balance control without using mesh division, a method in which a user selects a mode such as external light, fluorescent light, incandescent light in advance called a fixed mode or an achromatic color called one push auto, There are things to set.

[0003]

However, such conventional automatic white balance control is compatible with natural light (high color temperature in the daytime or low color temperature such as sunset), fluorescent light and incandescent light. For this reason, the setting of the achromatic color extraction range is wide, and subjects with the same color difference as the achromatic color under various light sources in the captured image (the skin color under the natural light source is similar to the achromatic color under incandescent light For example, when there is a color difference), an erroneous determination of an achromatic color is caused, wrong white balance control is performed on an image, and a color shift is caused. Also, the color temperature of artificial lights varies widely, and it is impossible to set the achromatic color extraction range at all color temperatures. Likely to cause. The present invention
In order to solve the above problems, an object of the present invention is to propose a white balance control device that allows a user to easily set and change an achromatic color setting during white balance control,
An object of the present invention is to provide a digital camera capable of photographing with a desired color balance by providing such a white balance control device. Also, by storing the achromatic color extraction range setting set by the user,
It is an object of the present invention to provide a white balance control device and a digital camera capable of setting an achromatic color extraction range suitable for a use environment of a user.

[0004]

According to a first aspect of the present invention, there is provided a white balance control apparatus for converting data obtained from an image sensor into color difference data, and converting the color difference data into a plurality of pieces of color difference data. In the white balance control device that divides the image into regions and determines achromatic color, and controls the white balance by adjusting the gain amount of the color data based on the pixel data of the region determined to be achromatic, It is characterized by comprising means for designating a supposed subject and photographing, and means for setting an area corresponding to the color difference data of the photographic data of the designated subject as an achromatic color extraction range. In the white balance control device according to a second aspect of the present invention, in the white balance control device according to the first aspect, the means for setting the achromatic color extraction range includes setting the achromatic color extraction range set by a user as a default value. It is characterized in that it is determined whether or not it is included in the achromatic color extraction range described above, and when it is not included, a warning is issued to the user. Claim 3 of the present invention
The white balance control device according to claim 1 or 2, wherein the means for setting the achromatic color extraction range is capable of sequentially setting a plurality of achromatic color extraction regions, It is characterized in that the color can be set as an achromatic color.
According to a fourth aspect of the present invention, there is provided the white balance control device according to the first, second or third aspect, wherein the data of a plurality of achromatic color extraction ranges set by a user is stored. At the time of photographing so that a selection can be made from the stored plurality of achromatic color extraction ranges. Also, claim 5 of the present invention
A digital camera according to any one of claims 1 to 4, further comprising a white balance control device according to any one of claims 1 to 4.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction and operation of an embodiment of the present invention will be described below in detail with reference to the drawings. (1) Configuration FIG. 1 is a block diagram showing a configuration of a white balance control device according to an embodiment of the present invention. The white balance control device includes a CCD 10, a CDS circuit 20, an A / D converter 30, a color interpolation unit 40, and an achromatic color extraction range setting unit 5
0, achromatic determination means 60, gain control means 70, and storage means 80. The CCD 10 is an image sensor such as a charge-coupled device, and converts an input image into an electric signal (analog image data). The CDS (correlated double sampling) circuit 20 is a circuit for reducing noise of a video signal input by the CCD 10. The A / D converter 30 converts the video signal reduced in noise by the CDS circuit 20 into digital data at an optimal sampling frequency (for example, an integer multiple of the subcarrier frequency of the NTSC signal). The color interpolation unit 40 complements the digital data converted by the A / D converter 30 from peripheral pixels to output three data of R (red), G (green), and B (blue) per pixel. . The achromatic color extraction range setting means 50 divides the color difference space into meshes in advance, and sets whether or not each of the mesh positions is an area to be determined as an achromatic color (the details of the setting method will be described later). In the achromatic color extraction range, the image data is included in any of the color difference (for example, Cr, Cb) axis division positions of the mesh-divided region based on data obtained by photographing an achromatic subject by changing the light source in advance. (See shaded portion in FIG. 2).
The achromatic color determination means 60 calculates color difference data from the three data of RGB output from the color interpolation means 40, determines which area the color difference data is divided into in the color difference space, and determines the data. If the pixel is included in the preset region of achromatic color, the RGB data of the pixel is integrated, and the count value is counted up. This determination is made for all pixels.

The gain control means 70 includes an achromatic color determination means 6
The integrated value of each of the RGB data calculated at 0 (each integrated value is R, G, B) and the count value (the count value is C
G / R, G / B operation or (G / R
C) / (R / C), (G / C) / (B / C) calculations are performed, and the calculation results are used as gain control values for AWB control, and gain control is performed on each of the RGB data.
AWB control (automatic white balance) is realized. (The calculation of the gain control value is described in Japanese Patent Application Laid-Open No. H11-20581.
See No. 2 publication. ) The storage unit 80 is a flash memory for storing default and photographing conditions set by the user. This also includes information on the achromatic color extraction range.

(2) Operation at the time of photographing FIG. 3 is a flowchart showing a schematic procedure of the operation at the time of photographing. The input image is converted into an electric signal of analog image data by an image sensor such as a charge-coupled device (step S100). The noise of the video signal converted into the analog image data is reduced by the correlated double sampling method (step S110). The low-noise analog image data is converted into digital data at an optimum sampling frequency (step S120). The digitized data is output as three data of RGB per pixel (step S130). The color difference data is calculated from the RGB data, and it is determined which area of the color difference space is divided into meshes, and the data is included in a predetermined area determined to be achromatic. Accumulates the RGB data of the pixel and counts up the count value (step S140). G / R, G / B operation or G / R calculation is performed based on the calculated integrated value of each of the RGB data (each integrated value is R, G, B) and the count value (the count value is C). (G / C) / (R /
C), (G / C) / (B / C) calculations are performed, and gain control is performed on each of the RGB data using the calculation results as gain control values, thereby implementing AWB control (automatic white balance) (step). S150).

(3) Method of Setting Achromatic Color Extraction Range FIG. 4 is a flowchart showing a schematic procedure for setting the achromatic color extraction range in advance. The user puts a part that seems to be achromatic under the light source to be photographed in a circular area provided in the center of the viewfinder (see FIG. 5), and presses a shutter button to set an achromatic color extraction range. Is input. The input image is converted into an electric signal of analog image data by an image sensor such as a charge-coupled device (step S200). The noise of the video signal converted into the analog image data is reduced by the correlated double sampling method (step S210). The low-noise analog image data is converted into digital data at an optimum sampling frequency (step S220).
Among the digitized data, data at the center of the image (a circular area at the center in the viewfinder) is extracted by sampling (step S230). The sampled data is output as three RGB data per pixel (step S240). This RGB
The color difference data (for example, Cr, Cb) is calculated from the data, and it is determined in which area of the color difference space the mesh is divided (step S250). For example,
One of the areas A where the color difference axis is divided into meshes as shown in FIG.
Is selected. It is checked whether or not the area selected in step S250 has the same value as the default setting of the achromatic color extraction range in the storage means 80 (step S260). When a mesh area other than the achromatic color determination range set by default is selected, a warning is displayed to the user by an LED or the like installed in the viewfinder or the like (step S270).

For example, it is assumed that a shaded area as shown in FIG. 7 is set as a default achromatic color extraction range. At this time, if the user specifies the position of A,
There is no warning because it is included in the default setting area. At the position B, an area that is not set in the default area is selected, and a warning is given that there is a possibility of a user setting error. By issuing such a warning, the user can confirm that the image selected as achromatic is correct or that a non-achromatic color is not mistakenly captured in the center area of the viewfinder when the shutter is pressed. Can be. If a mesh area within the achromatic color determination range set by default is selected, this area is set as an achromatic color extraction range and stored in the user setting area of the storage means 80 (step S280). If the user wants to set the area to be achromatic even when a warning is issued in step S270, the process proceeds to step S2.
The process proceeds to 80, and if the user is photographing the wrong area, the setting is not performed as the achromatic color extraction range (step S290). Therefore, since the color difference range set by the user can be set easily, it is possible to shoot with the white balance desired by the user.

(4) Processing by Mode Specification FIG. 8 is a flowchart showing a processing procedure for each mode of the camera. The user first sets whether to shoot or to set shooting conditions and the like by dialing, and reads the settings when the camera is turned on (step S300). As a result, a more detailed menu is displayed on a display unit such as a finder, and each processing is performed. When the photographing mode is selected by a dial or the like, photographing is performed, and the processing described in (2) is performed (steps S310 and S315). When the reading mode is selected by a dial or the like, the achromatic color extraction range set by the user is displayed in the viewfinder, and the setting value deemed appropriate for the current photographing is selected from the range to read out from the storage means 80. (Step S320,
S325). The read set values are stored in a flash memory or the like used for white balance control, and white balance control is performed on the captured video using the values. As described above, the user can select a plurality of setting values according to the shooting situation, so that the user can select an achromatic color extraction range setting suitable for the scene and shoot with a white balance desired by the user. When the setting mode is selected by a dial or the like, as described in (3), only one area of the area obtained by dividing the color difference axis into meshes is set as an achromatic color extraction range (steps S330 and S33).
5). In this mode, the achromatic color extraction range designated here is registered as new user setting in the storage means 80. At this time, it can be set separately from the already registered achromatic color extraction range. That is, it is possible to set so that a plurality of achromatic color extraction ranges can be stored, and one of them can be selected in the reading mode. When the addition mode is selected by a dial or the like, the achromatic color extraction range already registered in the storage means 80 is displayed in the finder, and the user selects from among the achromatic color extraction ranges and sets the achromatic color in the mesh area set as the achromatic color. Further, the storage unit 80 is updated by adding the area set this time (steps S340 and S345).

For example, as shown in FIG. 9, when the achromatic color extraction area set in the achromatic color extraction setting mode is A, and when the area B is selected in this additional mode, A and B Both are set as achromatic color extraction areas. Therefore, the achromatic color extraction range most suitable for the user's application can be set by sequentially adding the achromatic color extraction regions, so that it is possible to easily capture an image with the white balance desired by the user. When the clear mode is selected by a dial or the like, all or selected achromatic color extraction range settings registered in the storage unit 80 are cleared (steps S350 and S355). Thus, the unnecessary achromatic color extraction range can be deleted, and a new achromatic color extraction range setting can be registered. When another mode is selected by a dial or the like, for example, other exposure conditions, special shooting conditions, dates, and the like are set (step S360). Note that the processing for white balance control, the processing for setting the achromatic color extraction range, the selection of each mode, and the processing in the present embodiment can also be realized by a program using a microprocessor or the like.

[0012]

As described above, according to the present invention,
Since the color difference range set by the user can be easily set, shooting can be performed with the white balance desired by the user. Further, when a setting different from the default setting value is performed, a warning is issued to the user, and it is possible to prevent shooting in which the white balance is shifted.
Also, by sequentially adding a plurality of colors as the achromatic color setting area, it is possible to set the achromatic color extraction range setting that is most appropriate for the user's application, so that the user can easily shoot with a white balance more desired by the user. be able to. Further, since the user can set a plurality of achromatic color extraction ranges, the user can select an achromatic color extraction range setting suitable for the scene, and can shoot with a white balance desired by the user.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a white balance control device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of an achromatic color extraction range.

FIG. 3 is a flowchart showing a schematic procedure of an operation at the time of photographing.

FIG. 4 is a flowchart showing a schematic procedure when an achromatic color detection range is set in advance.

FIG. 5 is a diagram showing a circular area provided at a central portion in the viewfinder.

FIG. 6 is a diagram for explaining in which area of the mesh division the color difference data is included.

FIG. 7 is a diagram for explaining whether an achromatic color extraction range is included in a default setting area.

FIG. 8 is a flowchart showing a processing procedure for each mode of the camera.

FIG. 9 is a diagram for explaining an additional mode of achromatic color extraction.

[Explanation of symbols]

 Reference Signs List 10 CCD (charge coupled device) 20 CDS (correlated double sampling) circuit 30 A / D converter 40 Color interpolation means 50 Achromatic color extraction range setting means 60 Achromatic color determination means 70 Gain control means 80 Storage means

Claims (5)

[Claims] 1. A method for converting data obtained from an image sensor into color difference data, dividing the color difference data into a plurality of regions, determining an achromatic color, and using pixel data of the region determined to be achromatic. In a white balance control apparatus for controlling a white balance by adjusting a gain amount of color data, a means for designating a subject considered to be an achromatic color and photographing the same is equivalent to color difference data of photographing data of the designated subject. Means for setting an area portion as an achromatic color extraction range. 2. The white balance control device according to claim 1, wherein the means for setting the achromatic color extraction range is included in the achromatic color extraction range set by the user as a default value. The white balance control device is characterized in that it is determined whether or not it is included, and when it is not included, the user is warned. 3. The white balance control device according to claim 1, wherein the means for setting the achromatic color extraction range is capable of sequentially setting a plurality of achromatic color extraction areas so as to set a plurality of colors. A white balance control device characterized in that it can be set to an achromatic color. 4. The white balance control device according to claim 1, further comprising means for storing data of a plurality of achromatic color extraction ranges set by a user, wherein said plurality of achromatic color extraction ranges are stored during photographing. A white balance control device characterized in that it can be selected from a range of achromatic color extraction. 5. A digital camera comprising the white balance control device according to claim 1. Description: